Opioids misuse, abuse, addiction, and overdose are a serious public health crisis, and a leading cause of death in the USA. Complementary and integrative health (CIH) approaches to pain may help reduce opioid related harms. However, a 2016 VA QUERI ESP report stated that ?the evidence base regarding the effectiveness of select CIH interventions for reducing opioid use is extremely limited.? In addition, the Comprehensive Addiction and Recovery Act (CARA; PL 114-198) signed by Congress in to law on 7/22/2016 explicitly calls for ?expansion of research and education on and delivery of complementary and integrative health to veterans.? (Title IX, Subtitle C, Sec. 931). The impact of CIH on opioid use and pain-related outcomes in VA is poorly understood. Musculoskeletal disorders (MSD) and PTSD are two of the most prevalent disorders among Veterans in VA care, and their comorbidity is high: both are increasing, especially among women. Veterans with PTSD are at high risk for opioid related harms. Veterans with pain and PTSD are more likely to be prescribed opioids and benzodiazepines, and experience adverse outcomes. Because of the potential mutual reinforcement of PTSD and pain symptoms, CIH may help reduce opioid initiation and harms for many Veterans with PTSD. VA/DOD guidelines suggest a role for select CIH for both pain and for PTSD. The CDC Guideline for Opioid Therapy for Chronic Pain promotes non-pharmacologic treatments, making it likely that the demand for CIH will increase. However, the extent of CIH use among Veterans in VA care is not well-known, in part because most CIH data are contained in unstructured electronic health record (EHR) fields that defy ready quantification. We will examine CIH use and non-use among Veterans with MSD and compare opioid and pain outcomes by PTSD status. This is an opportunity to anticipate future needs for CIH and to examine patterns of benefit and harms. We will use algorithms from the Musculoskeletal Disorders cohort study (CRE12-012) to identify Veterans with MSD, and identify CIH use via structured data (e.g. CPT and ICD codes) and informatics tools on unstructured data (e.g. clinical notes). We will examine acupuncture, massage, meditation/mindfulness and yoga as they are currently or likely to be integrated into routine VA care. Using structured data only, we identified 7,621 CIH users among MSD cohort entrants in FY11-FY13 (n=309,277); of which, 21% had a PTSD diagnosis. Opioid and other medications will be identified from pharmacy data. Based on clinical observations, the benefit of CIH is not uniform. Some patients experience dramatic and long term pain relief, while others do not. Some benefit from one specific CIH modality versus another. To support personalized treatment and optimize future outcomes, we will also compare responses among pre-defined demographic and clinical sub-groups. Our specific aims are to assess the impact of CIH on opioid initiation among Veterans with MSD, estimate whether the effect varies by Veterans demographic and clinical characteristics, with particular attention to Veterans with a PTSD diagnosis, and to examine potential harms of CIH use, including new diagnoses of depressive disorders.